The present invention relates to posterior cervical fusion instrumentation and to posterior cervical fusion surgery.
The facet joint or “zygapophysial” joint is a synovial joint between the superior articular process of one vertebra and the inferior articular process of the vertebra directly above it. There are two facet joints in each spinal motion segment (right and left). The biomechanical function of each pair of facet joints is to guide and limit movement of the spinal motion segment. These functions can be disrupted by degeneration, dislocation, fracture, injury, instability from trauma, osteoarthritis, and surgery.
Posterior cervical fusion surgery has become a common procedure for the treatment of degenerative disease of the cervical spine. In such surgery, fusion hardware, including plates and/or screws, are installed along the cervical spine to stabilize the bones, thereby facilitating fusion of the neck. Posterior cervical fusion has been shown to stabilize the cervical spine after decompression and eliminate the long term risks of destabilization over time. However, current fusion hardware has considerable limitations due to the significant amount of soft tissue dissection required to place the hardware. While improved instruments and techniques have been developed for lumbar spine surgery, relatively fewer improvements have been developed in posterior cervical spine surgery.
Application of existing lumbar spine techniques to the cervical spine presents specific challenges that prohibit the simple modification of these techniques. For example, the anatomy of the cervical spine does not allow the safe placement of guide wires due to the vulnerability of the cervical spinal cord. Similarly, the presence of lateral masses and underlying vertebral arteries prohibit the use of canulated hardware.